docs: def _load_strain_sequences(self, strain_gempro):
          """Load strain sequences from the orthology matrix into the base model for comparisons, and into the
          strain-specific model itself.
  
          """
          if self._orthology_matrix_has_sequences:  # Load directly from the orthology matrix if it contains sequences
              strain_sequences = self.df_orthology_matrix[strain_gempro.id].to_dict()
          else:  # Otherwise load from the genome file if the orthology matrix contains gene IDs
              # Load the genome FASTA file
              log.debug('{}: loading strain genome CDS file'.format(strain_gempro.genome_path))
              strain_sequences = SeqIO.index(strain_gempro.genome_path, 'fasta')
  
          for strain_gene in strain_gempro.genes:
              if strain_gene.functional:
                  if self._orthology_matrix_has_sequences:
                      strain_gene_key = strain_gene.id
                  else:
                      # Pull the gene ID of the strain from the orthology matrix
                      strain_gene_key = self.df_orthology_matrix.loc[strain_gene.id, strain_gempro.id]
                      log.debug('{}: original gene ID to be pulled from strain fasta file'.format(strain_gene_key))
  
                  # # Load into the base strain for comparisons
                  ref_gene = self.reference_gempro.genes.get_by_id(strain_gene.id)
                  new_id = '{}_{}'.format(strain_gene.id, strain_gempro.id)
                  if ref_gene.protein.sequences.has_id(new_id):
                      log.debug('{}: sequence already loaded into reference model'.format(new_id))
                      continue
                  ref_gene.protein.load_manual_sequence(seq=strain_sequences[strain_gene_key], ident=new_id,
                                                        set_as_representative=False)
                  log.debug('{}: loaded sequence into reference model'.format(new_id))
  
                  # Load into the strain GEM-PRO
                  strain_gene.protein.load_manual_sequence(seq=strain_sequences[strain_gene_key], ident=new_id,
                                                           set_as_representative=True)
                  log.debug('{}: loaded sequence into strain model'.format(new_id))